1. Current Domestic and Aboard Clinical Applied Manual Tooth Preparation Technique.
In a conventional manual tooth preparation mode, it is difficult to meet standard requirements described in textbooks and clinical practices. The general level of manual tooth preparation in China is low (according to statistics from related experts, the qualified rate is about 40%). There is a lack of high-level dental doctors in China. Meanwhile, it often takes many years to cultivate a high-level clinician. These factors mentioned above together cause problems of “difficulties and high costs for accessing dental treatments”. Furthermore, there is thus an urgent need to research and develop a brand-new automatic and intelligent clinical tooth preparation technique to replace the conventional manual mode.
2. Laser Cutting Technique for Tooth Hard Tissues
Some commercial Er:YAG and Er:YSGG lasers have been used for simple handheld laser-type tooth preparation such as removal of dental caries and dental cavity preparation, but the tooth surface after being cut by Er lasers is uneven and coarse, probably accompanying with generation of microcracks, and thus cannot meet the high precision requirement of oral cavity reparation and tooth preparation. Laser cutting of tooth hard tissues is characterized by high precision, concentrated action, small thermal damage and the like, can perform cutting under very low energy density and has cutting thresholds of 0.6-2.2 J/cm2 and 0.3-1.4 J/cm2 respectively for dental enamel and dentin, so it is expected to be a digital control tooth preparation tool with high precision. However, it has been reported in literatures that the laser cutting rates with respect to dental enamel and dentin are respectively (0.05-3.6)×10−3 mm3/s and (0.12-1.90)×10−3 mm3/s, which are lower than those of a high-speed dental turbine handpiece (about 1 mm3/s). Meanwhile, different from a conventional mechanical grinding head, the laser has no force feedback in the operating process, which is unfavorable for an operator to sense the position, direction and gesture and the like of the cutting tool and thus is also unfavorable for controlling the precision of the cutting path.
3. Automatic Control Technique Related to Laser Optical Path in a Narrow Space
Currently, some digital control laser-scanning optical path control techniques have already appeared abroad. As an example, the three-dimensional laser processing software TbPs400 matched with the three-dimensional laser processing equipment from TRUMPF group (a large-scale laser equipment manufacturer, German) is only effective for cutting circular tubes and rectangular tubes, and strictly speaking, is a 2.5-dimensional laser process. Moreover, the three-dimensional laser processing software FORMA provided by PRIMAINUSTRIE S.P.A (a famous laser equipment manufacturing enterprise, Italy) can only be used on such working stations as IBMRISC Systern16000. The PEPS Pentacut 3D cutting system provided by CAMTEK Limited (UK) has a huge competitive advantage since it not only reduces the construction period but also provides higher precision, but such software is very expensive and thus cannot be widely spread in the market. By investigation of the more than 20 laser equipment manufacturers (including Han's Laser, Wuhan Farley Laserlab Cutting system Engineering Co., Ltd, Shanghai Tuanjie Baichao CNC Laser Co., Ltd, Shanghai Unity Prima Laser Machinery Co., Ltd, and other domestic famous laser equipment manufacturers) taking part in the 11th China internal machine tool exhibition (CIMT2009) held at April, 2009 in Beijing, it was found that the cutting machine tools exhibited by these exhibitors were substantially two-dimensional laser cutting machine tools, and only the Shanghai Unity Prima Laser Machinery Co., Ltd exhibited a three-dimensional laser cutting machine tool with the model number of SESAM02545, but the three-dimensional laser cutting automatic programming software matched with the same was the PEPS PentaCut developed by Camtek (UK). It demonstrates that currently domestic research of three-dimensional laser cutting equipment, particularly of an automatic programming system is still not sufficiently mature, which restricts the promotion of the three-dimensional laser cutting technique.
No related reports show that automatic control of a laser optical path has been realized for tooth preparation in a narrow space such as the oral cavity.